Closed vessel comprising a digital light deflection system

ABSTRACT

A digital light deflection system is disclosed where a group of alternating electrode pairs and prisms emersed in Kerr cell liquid is contained in a ceramic cylinder sealed at either end by a ceramic disc provided with a light-pervious window. The ceramic enclosure may be in the shape of a circular cylinder or may be a rectangular cylinder made up of rectangular plates sealed at their edges.

United States Patent 1191 Merz et al.

1 1 Apr. 2, 1974 CLOSED VESSEL COMPRISING A DIGITAL LIGHT DEFLECTIONSYSTEM [75] Inventors: Josef Merz, Hamburg, Germany;

Johannes van Esdonk; Joannes Franciscus Maria Janssen, both ofEmmasingel, Eindhoven, Netherlands [73] Assignee: U.S. PhilipsCorporation, New

York, N.Y.

[22] Filed: Nov.2, 1972 21 Appl. No.1 303,24

[30] Foreign Application Priority Data Nov. 6, 1971 Germany 2155269 [52]US. Cl. 350/160 R, 350/150 [51] Int. Cl. G02f 1/28 [58] Field of Search350/150, 160 R [56] References Cited UNITED STATES PATENTS 3,363,174l/l968 Hudson et a] 350/160 R 3,393,956 7/1968 Clark 350/160 R OTHERPUBLICATIONSv Ceramics by Walter H. Kohl, from Matls and Techniques forElectron Tubes, 1960, pp. 83-88.

Primary Examiner-Ronald L. Wibert Assistant ExaminerPaul K. GodwinAttorney, Agent, or Firm-Frank R. Trifari [57] ABSTRACT A digital lightdeflection system is disclosed where a group of alternating electrodepairs and prisms emersed in Kerr cell liquid is contained in a ceramiccylinder sealed at either end by a ceramic disc provided with alight-pervious window. The ceramic enclosure may be in the shape of acircular cylinder or may be a rectangular cylinder made up ofrectangular plates sealed at their edges.

3 Claims, 2 Drawing Figures CLOSED VESSEL COMPRISING A DIGITAL LIGHTDEFLECTION SYSTEM The invention relates to a closed vessel comprising adigital light deflection system consisting of a number of prisms and anumber of electrode pairs which are placed parallel according to thelongitudinal axis of the system and which are present in a suitableliquid (Kerr cells).

In digital light deflection systems a number of electrodes are providedat a proportionally small distance from each other while said electrodesobtain comparatively large potential differences relative to each other.Moreover, the liquid used for the Kerr cells, in this case nitrobenzene,must be extremely pure so that no contaminations from the wall of thevessel may dissolve in said liquid. Therefore, only quartz glass seemedto be suitable as a material for the wall. Quartz glass, however, hasseveral drawbacks. It is fragile and difficult to machine. Electrodelead-through conductors must also be passed through the quartz walls bymeans of intermediate glass or tubular members as a result of the largedifference in coefficients of thermal expansion of quartz glass andlead-through conductors. It has furthermore been found that impuritiesstrongly adhere to the quartz wall so that it is necessary to rinse thevessel with very pure nitrobenzene for 12 weeks so as to be able tomaintain the required purity of said liquid after closing the vessel.

It has been found that the above-mentioned drawbacks can be avoided forthe greater part in a closed vessel comprising a digital lightdeflection system consisting of a number of prisms and a number ofelectrode pairs placed parallel according to the longitudinal axis ofthe system and which are accommodated in a suitable liquid (Kerr cells)if, according to the invention, the wall of the vessel consists at leastpartly of a suitable ceramic material. Ceramic material which isvacuum-tight, for example, pure aluminum oxide, is preferably chosen.

The vessel may consist of a cylindrical part which is closed at the endsby means of discs which preferably also consist of a ceramic materialand in which a lightpervious window is provided. However, it isaltematively possible to build up the vessel from a number ofrectangular plates which are secured together with their edges by meansof a suitable metal or soldering material. by diffusion or soldering.The cross-section of the vessel may in that case be a polygon,preferably a rectangle. A soldering material is to be understood to meana meltable material which readily adheres to the ceramic material andhas a sufficiently low melting temperature. Particular vitreousmaterials are very suitable but metal-containing materials may also beused, provided they do not dissolve in the liquid present in the vesseland do not react with it.

The invention will be described in greater detail with reference to thedrawing, in which FIG. 1 shows, partly broken away, a vessel accordingto the invention having a cylindrical cross-section and FIG. 2 shows thecomposing parts of a vessel having a prismatic cross-section.

Reference numeral 1 in FIG. 1 denotes a cylindrical part of a vesselwhich consists of a ceramic material and which is closed by ceramicdiscs 2 and 3 in which light-pervious sapphire windows 4 and 5 areprovided.

In the vessel 1 is arranged a digital light deflection system consistingof prisms 6 and Kerr cells consisting of electrode pairs which areplaced parallel to the longitudinal axis of the system and which aresecured to leadthrough conductors 10. Furthermore, two metal exhausttubes 8 are present.

The end faces of the cylindrical ceramic part 1, the surfaces of theclosing discs 2 and 3 to be connected as well as the holes 9 for themetal exhaust tubes 8 are previously metallized, for example, byproviding a layer of a mixture of 80 percent by weight of molybdenumoxide and 20 percent by weight of a mixture consisting of:

13 percent by weight A1 0 35 percent by weight SiO and 52 percent byweight MnO.

This layer is burnt-in in a moist protective gas atmosphere at l,400 Cfor 30 minutes in a furnace. The lead-through conductors 10 are thensealed in holes which are drilled in the wall of the part 1 at l,300 Cfor 10 minutes while using a vitreous soldering material consisting of:

37 percent by weight MnO,

percent by weight SiO and 13 percent by weight A1 0 The end faces of thepart 1, the lead-through conductors l0 and the inner wall of the holes 9for the exhaust tubes 8 are then nickel-plated (thickness nickel layer 5to 6 .4.). The electrodes 7 are then provided in the part 1 of thevessel by means of moulds. The electrodes 7 are then soldered to thelead-through conductors l0 and the exhaust tubes 8 are soldered in theholes 9, for example, with silver-copper soldering material by heatingin a furnace at 850 C. The prisms are then mounted in the tube. Theclosing discs 2 and 3 are then secured to the end faces of the wall 1 bydiffusion of the nickel layers or by means of a soft-soldering materialconsisting of 40 percent by weight lead and percent by weight tin at 450C. The windows 4 and 5 consist of sapphire and are previously secured inthe discs 2 and 3 by means of the above-mentioned vitreous solderingmaterial at l,300 C.

The tube is then evacuated and tested for vacuumtightness. The liquid,in this case nitrobenzene, is then pumped into the vessel through onetube 8 and removed through the other tube 8 and the tube is thus rinsedso as to remove impurities out of the vessel. Contrary to allexpectations, it has been found that when a ceramic wall consisting ofA1 0 is used, a rinsing time of 3 days is already sufficient in contrastwith a rinsing time of 12 weeks which is necessary when a quartz glasswall is used. The metal tubes 8 are then sealed by means of sealed glassparts 11 and 12.

In the embodiment shown in FIG. 2, the vessel consists of a number ofceramic plates which are secured together. First the holes 17 and 20 aredrilled in the plates 15, 13 and 16. The bottom plate 13 is then securedto the side plates 14 and 15 by means of a vitreous soldering materialhaving a melting temperature of 1,500 C and consisting of:

54 percent by weight A1 0 38.5 percent by weight CaO, and 7.5 percent byweight MgO. t The pulverulent mixture of said substances is stirred to athin slurry with a solution of nitrocellulose in butyl acetate. Saidslurry is spread on the surfaces of the plates 13, 14 and 15 to beconnected together and is dried. The plates 14 and 15 are then placed onthe bottom plate 13 and the assembly is heated in a furnace at l,500 Cfor 30 minutes after which the vitreous soldering material 21 resultingfrom the slurry has connected said plates to form a U-shaped member. Theend faces 18 of the plates l3, l4 and 15 are then ground flat whileusing a mould. The end faces 18, the upper surfaces 22 of the plates 14and I and strips 19 on the upper plate 16 and also the inner surface ofthe holes 17 are then metallized as described with reference to FIG. 1.Lead-through conductors are then sealed in the holes 20 by means of thevitreous material described with reference to FIG. 1 which has a meltingtemperature of l,300 C, after which the metallized surfaces as well asthe lead-through conductors are nickel-plated. Mounting of the exhausttubes 8 and the electrodes 7 is carried out in the same manner asdescribed with reference to FIG. 1. The prisms, however, can now bemounted in a much simpler manner in the open U-shaped member and on theplate 16. The plate 16 is then placed on the U-shaped member and thenickel-plated surfaces 19 and 21 are connected together, for example, bydiffusion or soldering.

In order to obtain the desirable measuring accuracy of the electrodedistances, known measures will be taken in general, for example,providing raised fitting edges on the surfaces 21 and 19 to be connectedby soldering and/or providing soldering material only over a part of thewidth of the edge in such manner that the thickness of the layer ofsolder has no influence on the distance between the bottom plate 13 andthe upper plate 16.

The tube having a rectangular cross-section is then closed with circulardisc-shaped or rectangular closing plates not shown, which may be madeto be detachable so as to be able to perform repairs of the electrodesystem afterwards.

What is claimed is:

1. A digital light deflector, comprising a plurality of substantiallyrectangular ceramic plates connected at the major edges to form arectangular cylinder, vacuum-tight seals at the connection areas of theplates, a plurality of substantially flat electrode pairs havingparallel major surfaces and fixed in a spaced relationship along theinside of the cylinder, a plurality of prisms fixed between eachelectrode pair, Kerr cell liquid substantially filling the cylinder andsurrounding the electrodes and prisms, and a separate light-perviousmember vacuum sealed to each end of the cylinder.

2. A digital light deflector as claimed in claim 1, wherein the ceramicplates are composed of aluminum oxide.

3. A digital light deflector as claimed in claim 1, wherein eachlight-pervious member comprises a ceramic disc provided with alight-pervious window.

CERTIFICATE OF CORRECTION Dated April 2. 1974 Patmn No. 3,801,184

Inventor(sXIo MARIA JANSSEN It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

ON THE TITLE PAGE '"[30] Foreign Application Priority Data Nov. 6, 1971Germany......,...2l55269" should read [30] Foreign Application PriorityData Nov. 6, 1971 Germany .......P.2l55269.2-;

IN THE SPECIFICATION Col. 1, line 12, after "other" insert a comma.

Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents $22 3? UNITED STATES PATEN" OFFICE CERTIFKQATE 0F CORRECTIONPatent No. 3 I 801 184 Dated il 2 9 Inventor(s) 0 E MARIA JANSSEN It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

ON THE TITLE PAGE [30] Foreign Application Priority Data Nov. 6, 1971Germany. ..2l55269" should read -[30] Foreign Application Priority DataNov. 6, l9 7l Germany ..P.2l55269.2;

IN THE SPECIFICATION Col. 1, line 12, after "other" insert a comma.

Signed and sealed this 1st day of October 1974.

(SEAL) Attest:

C. MARSHALL DANN McCOY M. GIBSON JR.

Commissioner of Patents Attestin-g Officer

1. A digital light deflector, comprising a plurality of substantiallyrectangular ceramic plates connected at the major edges to form arectangular cylinder, vacuum-tight seals at the connection areas of theplates, a plurality of substantially flat electrode pairs havingparallel major surfaces and fixed in a spaced relationship along theinside of the cylinder, a plurality of prisms fixed between eachelectrode pair, Kerr cell liquid substantially filling the cylinder andsurrounding the electrodes and prisms, and a separate light-perviousmember vacuum sealed to each end of the cylinder.
 2. A digital lightdeflector as claimed in claim 1, wherein the ceramic plates are composedof aluminum oxide.
 3. A digital light deflector as claimed in claim 1,wherein each light-pervious member comprises a ceramic disc providedwith a light-pervious window.